DESCRIPTION (Applicant's abstract): Item memory is memory for occurrence of events (e.g., Was this word spoken?). Source memory is memory for the source of an occurrence (e.g., Did A say it?). There is evidence that source memory is particularly vulnerable to aging and that it is differentially affected by different types of brain damage (e.g., frontal versus temporal). Signal Detection Theory has to date been extensively applied to item memory but has not been applied to source memory. When extended to cover source memory, it offers new and interesting predictions concerning the relation between source and item memory. The implications of Signal Detection Theory for performance of normal participants will be tested. The results will be compared with the results predicted by a different approach to memory, the family of threshold theories. The Signal Detection Theory will be applied then to evaluate the effects of aging and specific brain damage on memory.